Improved bobbin winding method and winding machines for its implementation

Abstract: An improved method and device for winding yarn (5) into bobbins (15), in which the yarn (5) is cut on command such as to make its cut end wind onto the central portion of the surface of the bobbin (15) under formation, in order to facilitate restoration of yarn continuity and restart of winding.

Description: This invention relates to an improved method for collecting yarn in automatic winding machines according to the preamble of claim 1 and to an improved device for implementing said winding method according to the preamble of claim 4. The invention relates particularly to yarn winding after its controlled cutting, this winding being required to take place within the central portion of the bobbin. It is known in the art that winding machines in general, and bobbin winding machines in particular, are provided with bobbin carrying arms. These arms consist essentially of a mandrel formed from a fixed fixing centre and a movable fixing centre, the purpose of which is to carry, centre and fix the tube onto which the yarn is wound to form the bobbin, and to allow regular yarn winding. The bobbin assumes either substantially cylindrical or substantially frusto-conical shapes. Frusto-conical shapes are often formed in order to facilitate yarn unwinding during the subsequent fabric manufacture stages. At each request for controlled yarn cutting it can happen that the yarn end is winding onto one of the two ends of the bobbin under formation and, suite frequently, that the yarn - having its cut end suddenly without tension and uncontrolled - deposits in the form of several turns about one of the fixing centres of the yarn carrying mandrel. Alternatively, that yarn portion which escapes from the side of a frusto-conical bobbin deposits about the circumferential gripping line between the fixing centre and the end of the tube. During the next joining or knotting cycle it can happen that not all the yarn turns wound on the fixing centre are gripped, unwound and removed by the suction port; on restarting the winding process the bobbin under formation again accumulates wound yarn, but there remains the presence of a more or less lengthy yarn portion extending beyond the side of the bobbin. Even worse happens if the suction port is unable to suck-in the yarn end because it is too distant. The unit is then compelled to stop, to interrupt the winding process and to require the assistance of a service operator. The cost of this assistance and the reduction in the machine service factor considerably influence the production cost calculation. The efficiency of service operators is very low due to the randomness of the operations as opposed to programmed intervention. A further serious drawback arises from the yarn portions extending outside the bobbin, which can compromise correct use of the bobbin during its unwinding in subsequent processing. DE-A-40 25 696 discloses a method and device for winding yarn, in which the yarn is cut on command such as to make its cut end wind onto the central portion of the bobbin under formation, but detecting the position of the wound yarn by a yarn sensor and giving the consent to said command only when such yarn is in the desired position . In this connection it should be stated that DE-A-4025696 discloses a device in which the "Garnsensoren" appear to consent or deny to proceed with the cutting members but they do not carry out any calculation on the moment T o in which the cut is to be made. The object of the present invention is to remedy the aforesaid drawbacks by providing a method and devices for its implementation, which enables controlled yarn cutting to be effected at the required moment and the cut yarn to be deposited within a central portion of the bobbin under formation. The invention is directed towards eliminating portions extending outwards from the bobbin sides following controlled cutting and preventing the yarn end becoming positioned in regions close to its ends. The improved yarn winding method of the present invention comprises the features of the characterizing part of claim 1. In this manner the precise moment of cutting which enables the yarn end to be wound onto a central portion of the bobbin under formation can be determined. In other words, the delay which has to take place between the cutting request and its implementation is exactly determined at any given time. The characteristic values of the winding yarn are those values indicative of its elasticity and count. They are fed into the machine control unit via a control keyboard at the commencement of a new process. The length of the free end on cutting is the distance between the cutting means and the upper winding point. The improved device for implementing the winding method claimed in claim 1 further comprises the features of the characterizing part of claim 4. The invention is described hereinafter in terms of a typical implementation in a bobbin winding machine in which the bobbin drive roller is provided with yarn guide grooves for controlling traversing, as shown in Figures 1 and 2. Typically, yarn winding is carried out at very high speed, of the order of 1000 m/min or more, meaning that the yarn clearer is traversed by the yarn at a speed of the order of 20 m/sec. In this embodiment the control unit is a minicomputer which processes the electrical pulses generated by the probe disc to measure the roller revolutions or revolution fractions, and the pulses generated by a proximity sensor which identifies the position of the yarn within its continuous to-and-fro traversing. In one embodiment the probe disc is used as a transducer for the effective yarn winding speed, as a transducer for the yarn length effectively wound per unit of time, and for measuring the angular position of the drive roller for the bobbin under formation. In a further embodiment the said yarn proximity sensor is used as a transducer for the axial position, moment by moment, of the yarn winding point on the bobbin surface. The apparatus of the present invention, in the sense of a coordinated assembly of sensing means, control and processing units and operating members, can also be advantageously associated with members for regularizing the winding process, such as bobbin modulation members for preventing the formation of ribbing on the bobbin. Figure 1 shows the implementation of the invention in a bobbin winding machine with a yarn guide roller, and represents a schematic front view of the winding unit with the means for measuring the winding parameters and the connection lines to the control and processing unit. Figure 2 shows the angular positions of the winding yarn during its to-and-fro movement within the helix of the grooved roller and also shows the presence of a yarn defect which activates the cutting request at a precise moment, such as to enable the cut end to be wound onto the central portion of the bobbin. In the various figures equal reference numerals correspond to equal elements. The figures show the following constituent elements: 14 is the toothed transmission belt between the drive source (not shown) and the drive roller 3 provided with a yarn guide groove; 15 is the bobbin under formation, wound with crossed yarn by the simultaneous action of the yarn guide element and the rotational drive by the roller 3; 11 is the bobbin carrying arm which maintains the bobbin 15 in position as its diameter increases, the drive roller 3 transmitting both rotary motion to the bobbin and reciprocating axial movement - by virtue of its grooves - to the yarn 5 fed to the bobbin; 2 is the probe disc which measures moment by moment the rotational speed of the roller 3 during the entire bobbin formation process; 18 is the unwinding package which feeds the yarn 5; 6 is a proximity sensor, for example of inductive or similar type, to determine the angular position - in the plane of the figure - of the yarn 5 under rapid periodic reciprocating movement; 4 is a sensor, or clearer, for monitoring the yarn in order to detect and evaluate the defects in the yarn running within it. On detecting yarn defects 30 exceeding a preset threshold value the sensor 4 emits cutting command pulses; 1 is the control unit based on a minicomputer or electronic card able to memorize and implement the instructions of the operator, which are fed in via the control keyboard 8. Said unit 1 is arranged to transform the instructions originating from the cable 9 into a programme executed in its computing and processing centre in order to provide moment by moment the signals required during the winding process. Typically the unit 1 comprises a microprocessor which uses as input both the information from the sensors 4 and 6 via the cables 7 and 12 and the information from the probe 2 via the cable 10, to feed the cutting pulse to the elements of the block 16 each time the yarn 5 shows an undesirable defect. The control unit is also fed with data concerning the quality of the bobbin to be produced. Such data typically consist of the bobbin geometrical values and the values of undesirable defects to be eliminated during winding. The minicomputer serving each winding unit is connected to the central control or processing unit of the overall machine, in which the control keyboard is located. In the following description of the method, reference is made mainly to its novel aspects within the framework of a single winding unit associated with the means for determining the exact moment of cutting and its implementation. In a automatic bobbin winding machine consisting of a number of winding units arranged side by side, the yarns from the feed packages are collected in the form of a cross-turn bobbin 15 to be used in subsequent processing. Simultaneously with the transfer of yarn from the package 18 to the bobbin 15, the yarn is subjected to scanning or monitoring by the control block 16 which in a preferred embodiment of the invention can be an electronic yarn clearer, already known in the art. Yarn clearing members are used in bobbin winding to remove any portions of the yarn running into the winding machine at high speed which comprise defects 30 in terms of the transverse dimension of the yarn. Such defects relate to yarn portions which locally fall outside a determined count range and/or show substantial count variations which however lie within said range but extend over a significant length or occur with a unacceptable frequency. For inserting the parameters required for detecting and analyzing defects, analysis circuits are provided connected to the feeler means or sensor 4, which unequivocally feeds one or more electrical sensor pulses to the control unit 1 via the cable 7. Said pulses are advantageously preamplified to relate them to and process then with the electrical pulses generated by the proximity sensor 6 and by the probe disc 2, and with the characteristic values of the yarn 5 and of the type of bobbin 15 to be obtained. All the arriving pulses are compared and processed moment by moment in the computing centre of the minicomputer. The electronic yarn clearing block or device 16 can be of conventional construction and can contain an electrical or capacitive transducer as the feeler or scanner device. It produces an electrical feeler signal corresponding to a transverse dimension, ie an instantaneous cross-section or diameter, or a count or mass per unit length of yarn. This signal is preamplified - in direct current or alternating current - and fed to the measurement part. Said part normally comprises circuits in which those signals exceeding a determined threshold value (unacceptable defect) or are below this value (acceptable defect) are further processed. The analysis circuit detects, measures and analyzes the defects 30 in the yarn 5 and, when signals corresponding to undesirably large, long or frequent defects arise, produces a determined output pulse which is fed to the control unit 1. Said control unit 1 processes the cutting request pulse together with the other pulses and values and at a precise moment operates the cutting means of the block 16. The yarn is cut in such a manner as to cause it to wind onto the central region of the bobbin 15, ie within the angular space 20 defined by the limits 22 and 21 of Figure 2. Said angular space 20 represents a winding parameter which is also fed into the memory of the minicomputer of the control unit 1. The proximity sensor 6, of known type, provides an electrical signal, ie a control pulse, which corresponds to the instantaneous angular position 24 of the yarn 5 and its direction of movement in the direction of the arrows 23 and 19, or 25. As stated, the yarn 5 is subjected by the grooves of the roller 3 to rapid angular reciprocation between the ends 28 and 29, these being substantially symmetrical about the vertical centre line 27, from which they are spaced by an enclosed angle 26. The signal provided by the proximity sensor 6 is processed in association with the signal originating from the probe disc 2, which measures the rotational speed of the roller 3 and hence of the yarn collection speed on the bobbin 15 under formation, in order to continuously determine within the unit 1 the time taken by the yarn to undergo the angular movement required to again enter the reference position 29, at which it assumes its minimum distance from the sensor 6. On passage of an undesirable and unacceptable defect 30, or if a generated cutting request arises (for example because the bobbin is complete), the control unit 1 receives a cutting pulse at its - input and calculates in its computing centre a precise moment T o in which to make the cut so that the cut yarn end winds within the angular aperture 20. This is calculated on the basis of the winding speed, the "catapulting" time Δt for the yarn end, time lags in the operation of the cutting members, the angular position of the yarn and the direction of yarn movement. The said yarn "catapulting" consists of the elastic reaction of the type of yarn being processed, when cut. Following cutting of the yarn 5, its end is subjected to the elastic energy accumulated by the effect of the winding tension. At the moment of cutting, the yarn end between the winding point on the bobbin 15 and the cutting point "catapults" more rapidly than the winding speed. This more or less elastic behaviour is a parameter which is predetermined and is fed into the unit 1 by the operator. Cutting at time T o , which corresponds to the correct position of the yarn within the angular sector 20 at the moment of cutting, can involve a certain time lag between the cutting request signal and the cut itself. This lag is very small but because of the high linear winding speed is significant in terms of the length of yarn which passes between the time the defect is detected and the time the cut is effected. According to a preferred embodiment of the invention, the subsequent joining operation is conducted taking account of this possible yarn length, by suitably determining the suction time of the yarn pick-up ports on the bobbin side. Figures 3 and 4 show an alternative embodiment of the bobbin winding machine with a separately operating yarn guide. Those members of Figures 3 and 4 which have the same significance and function as those described with reference to the embodiment shown in Figures 1 and 2 carry the same reference numerals. Those members peculiar to the alternative embodiment are shown, where: 33 is a control box containing the drive means for the rod 37, which is driven with periodic transverse reciprocating movement in accordance with the arrows 31 and 35; on said rod 37 there is fixed as an unseparated body the yarn guide 38, comprising an eyelet for retaining the yarn and for moving it continuously to and fro between the end positions 38a and 38b of the yarn guide, corresponding to the end positions of the yarn 5a and 5b; the proximity sensor 6 is in this case located in correspondence with the limit stops 34 and 32 positioned on the rod 37; the cable 36 connects the control box 33 to the control unit 1. In this embodiment the moment of yarn cutting is determined on the basis of the position of the yarn guide 38 within the angular sector 20. The yarn end to be catapulted is that lying between the yarn guide element 38 and the cutting point within the block 16.

Claims: An improved method for collecting yarn in an automatic winding machine, such as automatic bobbin winding machines, preferably consisting of a plurality of side by side winding units in which the yarn is wound as cross-yarn bobbins by the simultaneous action of a drive roller (3) and a yarn guide element which induces a traversing movement in the yarn (5), such method being directed to collect the end of the cut yarn on the central portion of the bobbin under formation when the yarn is caused to be cut by cutting members of the winding units, and including the steps of: determining the position of the winding yarn on the bobbin (15) under formation, which moment by moment changes its angular position (24) in the frontal plane of the winding machine within a sector (28-29) with continuous to-and-fro reciprocating traversing movement; feeding into the machine control unit (1) the characterising values for the bobbin under formation, consisting of values representing the yarn being wound, the desired bobbin quality; preparing in said machine control unit (1) the required yarn cutting request signals, following the presence of an undesirable defect, on the basis of said characterising value for the bobbin under formation, characterised by further comprising the steps of: continuously and simultaneously measuring both the yarn winding speed and its transverse speed during its traversing movement; continuously and simultaneously detecting the angular position (24) of the yarn (5) and its direction of movement; transmitting the information from the sensors for said measurements and detection to the computing centre of the machine control unit (1) to exactly calculate, on the basis of the values of the speed measurements, of the detected angular position and direction of movement of the yarn, and of the length left free on controlled cutting of the yarn, the time for cutting the yarn such that the yarn end left free after cutting winds on a central portion of the bobbin within a frontal angular sector (20). An improved method for collecting yarn in an automatic winding machine, such as automatic bobbin winding machines, as claimed in claim 1, characterised in that the characterising values for the type of yarn being wound are values indicative of the elastic behaviour of the yarn and its count, said values being predetermined and being fed into the control unit via a control keyboard. An improved method for collecting yarn in an automatic winding machine, such as automatic bobbin winding machines, as claimed in claim 1, characterised in that the characterising values for the bobbin quality consist of geometrical bobbin values and values representing the allowable yarn count variation range, the control unit eliminating those yarn portions which locally fall outside a determined count range or present substantial count variations contained within said range but of a significant length or with an unacceptable frequency, based on the analysis of defects indicated by a yarn feeler means which provides the machine control unit with electrical pulses unequivocally corresponding to the detection of defects. An improved device for implementing the winding method claimed in claim 1, preferably consisting of a plurality of side by side winding units, comprising: means for determining the position of the winding yarn on the bobbin (15) under formation, which moment by moment changes its angular position (24) in the frontal plane of the winding machine within a sector (28-29) with continuous to-and-fro reciprocating traversing movement; means for feeding into the machine control unit (1) the characterising values for the bobbin under formation, consisting of values representing the yarn being wound, the desired bobbin quality; means for monitoring yarn defects and controlled yarn cutting means, grouped within the yarn clearing block (16) ; said means being associated with a control unit (1) , characterised by further comprising : means for continuously and simultaneously measuring both the yarn winding speed and its traversing speed during its traversing movement ; means for continuously and simultaneously detecting the angular position (24) of the yarn (5) and its direction of movement ; said means being associated with the control unit (1) which processes the determined working parameters for the process underway and the signals received from said measuring and detecting means to exactly calculate the time for cutting the yarn, and when a yarn cutting signal arises provides a control signal to the cutting means so that they act at that precise moment which enables the cut yarn end to wind onto a central portion of the bobbin under formation. An improved winding machine as claimed in claim 4, characterised in that the means for instantaneously measuring the winding parameters comprise a probe disc (2) for measuring both the rotational speed and the angular position of the drive roller (3), and a proximity sensor (6) which provides moment by moment a signal identifying the angular position of the winding yarn during its traversing reciprocating movement. An improved winding machine as claimed in claim 4, characterised in that the probe disc (2) is used as a transducer for the effective yarn winding speed, as a transducer for the yarn length effectively wound per unit of time, and as an element for measuring the angular position of the drive roller (3). An improved winding machine as claimed in claim 4, characterised in that the proximity sensor (6) is used as a transducer for the axial position, moment by moment, of the yarn winding point on the bobbin. An improved winding machine as claimed in claim 4, characterised in that the yarn guide element consists of a spiral groove provided on the bobbin drive roller (3), the proximity sensor being a yarn sensor (6) located in proximity to the reversal point of the traversing movement, so that the sensor is at its minimum distance from the yarn when the yarn (5) reaches its movement reversal point (29). An improved winding machine as claimed in claim 4, characterised in that the yarn guide element consists of a yarn guide positioned on a rod (37) driven with reciprocating motion in a direction parallel to the drive roller axis (3), the proximity sensor (6) being a sensor associated with two limit stops (32, 34) located on said rod and corresponding to the reversal points (38a, 38b) of the traversing movement, so that the sensor (6) is at its minimum distance from one of the limit stops (32, 34) when the yarn reaches one of its movement reversal points (5a, 5b). An improved winding machine as claimed in claim 4, characterised in that the control unit (1) of each individual winding unit is a minicomputer or microprocessor connected to the machine central control unit into which the data relative to the process underway are fed via a control keyboard (8), said minicomputer processing the signals generated by a probe disc (2) which measures both revolutions and revolution fractions of the bobbin drive roller, the signals generated by a proximity sensor (6) which identifies the angular position of the yarn during its traversing reciprocating movement, and the signals from the monitoring of the yarn within the yarn clearer (16) for detecting its defects, in order to provide the yarn cutting command at the required moment for the cut yarn end to be wound onto a central surface portion 20 of the bobbin under formation.

Inventors: BADIALI ROBERTO, CLAUT DEMETRIO, MARANGONE NEREO, BADIALI, ROBERTO, CLAUT, DEMETRIO, MARANGONE, NEREO
Applicants: SAVIO MACCHINE TESSILI SPA, SAVIO MACCHINE TESSILI S.P.A.
Application year: 1994
Main classification: B65H63
IPC codes: B65H63